Headgear tensioning for respiratory mask

ABSTRACT

Headgear for a patient interface includes at least one headgear strap and an indicator provided to the at least one headgear strap structured to indicate attainment of a desired adjustment setting of the headgear in response to headgear tension applied to the at least one headgear strap.

CROSS REFERENCE TO APPLICATIONS

This application claims the benefit of Australian ProvisionalApplication No. AU 2006905236, filed Sep. 21, 2006, which isincorporated herein by reference in its entirety.

BACKGROUND OF THE INVENTION

1. Field of the Invention

The present invention relates to a headgear assembly for use in holdinga patient interface such as a respiratory mask in position on apatient's face, the patient interface being used in the treatment, e.g.,of Sleep Disordered Breathing (SDB) with Non-Invasive Positive PressureVentilation (NIPPV).

2. Description of Related Art

Respiratory mask assemblies for treatment of SDB such as ObstructiveSleep Apnea (OSA) are typically secured to the patient's head by meansof a headgear assembly.

Headgear assemblies are structured to position and stabilize a patientinterface, such as a nasal mask, on a patient's face so that a good sealcan be maintained. A headgear assembly typically includes a pair of sideportions, and a rear portion. The side portions are adapted to engagewith the patient's mask, and the rear portion is adapted to engage theback of the patient's head.

Prior art headgear arrangements typically have side straps typicallyheld in position using hook and loop material, for example VELCRO®, bypassing an end of the strap through a loop on the mask—or on a connectorwhich connects to the mask—and then folding it back onto itself. In thisway, the strap can be adjusted to adjust the headgear tension and thusthe force which the headgear applies to hold the mask against thepatient's face, to suit the particular needs of the patient in orderthat a comfortable effective mask seal be effected.

Correct adjustment of the headgear tension is important to the successof the therapies and to achieving patient compliance with the therapyregime.

Currently, patients generally use mask comfort to determine the headgeartension adjustment. However, the time period over which the patient isadjusting the tension is short in comparison with the length of eachtherapy session, and what feels comfortable over a 5 or 10 minuteadjustment period will often be too tight to maintain comfort over an 8hour therapy session. Also, changes in treatment pressure at the maskmay require different headgear tension settings for optimal performance.

The ideal headgear tension is the loosest possible to maintain a sealbetween the mask cushion and the patient's face. However, it isintuitive for the patient to continue to tighten the headgear straps toseek to eliminate mask leak completely. In some instances,overtightening of the headgear may crush the sealing cushion of the maskand in fact increase the leak.

Furthermore, overtightening may cause patient discomfort, marking orcreasing of the patient's face and neck which is visible the next day,and may lead to sores and tissue necrosis. Other possible effects ofovertightening include dental and gum impairment, and pressure on thetemporomandibular joints causing headaches, increased occurrence ofapnea, or a reduction of nasal passage area leading to increasedbreathing resistance. All of these may make the therapy unpleasant forthe patient and may lead to non-compliance with the therapy by thepatient.

Alternatively, insufficient headgear tension may lead to mask leak byfailure to maintain a seal between the mask and the patient's face, ormovement of the mask while the patient sleeps, which may limit thesuccess of the therapy or may wake the patient and lead to the patientdiscontinuing the therapy.

SUMMARY OF THE INVENTION

One aspect of the present invention relates to a headgear assembly forattachment to a patient interface that delivers breathable gas to apatient such as a respiratory mask to a patient's face, including

a headgear body adapted to fit to the patient's head and has connectionportions adapted for connection to the patient interface,

adjustment means for adjusting said headgear, and

indicating means responsive to an adjustment parameter of the headgearfor indicating attainment of a desired adjustment setting of theheadgear.

Another aspect of the invention relates to a patient interface adaptedto deliver breathable gas to a patient and adapted for attachment to thepatient by means of adjustable headgear, including indicating meansresponsive to an adjustment parameter of the headgear for indicatingattainment of a desired adjustment setting of the headgear.

Another aspect of the invention relates to a headgear assembly forattachment to a patient interface that delivers breathable gas to apatient, including:

a headgear body adapted to fit to the patient's head and havingconnection portions adapted for connection to the patient interface;

an adjustment mechanism to adjust the headgear body, and

a limiter to limit tightening adjustment of the headgear body.

Another aspect of the invention relates to a headgear assembly forattachment to a patient interface that delivers breathable gas to apatient, including:

a headgear body adapted to fit to the patient's head and havingconnection portions adapted for connection to the patient interface,

an adjustment mechanism to adjust the headgear body, and

a control mechanism to control adjustment of headgear tension.

Another aspect of the invention relates to a method for controllingadjustment of headgear. The method includes adjusting the headgear andvisually indicating attainment of a desired adjustment setting of theheadgear.

Another aspect of the invention relates to a connector arrangement for apatient interface. The connector arrangement includes a connectorprovided to a mask and a clip provided to headgear. The clip is adaptedto connect to the connector in a multiple stage arrangement such thatrelease of the clip from one stage to an adjacent stage indicatesattainment a desired headgear tension.

Another aspect of the invention relates to headgear for a patientinterface. The headgear includes at least one headgear strap and anindicator provided to the at least one headgear strap structured toindicate attainment of a desired adjustment setting of the headgear inresponse to headgear tension applied to the at least one headgear strap.

Another aspect of the invention relates to a connector arrangement for apatient interface. The connector arrangement includes a connectorprovided to a mask and a clip provided to headgear. The clip is adaptedto connect to the connector such that excessive tension applied to theclip allows the clip to completely release from the connector.

Another aspect of the invention relates to a method for controllingheadgear tension. The method includes connecting headgear straps ofheadgear to a mask and releasing tension upon application of excessivetension force to the headgear straps.

Further aspects of the invention relate to a patient interface andheadgear combination, and a method of controlling adjustment of aheadgear for a patient interface.

Other aspects, features, and advantages of this invention will becomeapparent from the following detailed description when taken inconjunction with the accompanying drawings, which are a part of thisdisclosure and which illustrate, by way of example, principles of thisinvention.

BRIEF DESCRIPTION OF THE DRAWINGS

The accompanying drawings facilitate an understanding of the variousembodiments of this invention. In such drawings:

FIG. 1 is a front perspective view of a prior art MIRAGE® full faceheadgear and mask arrangement;

FIG. 2 is the MIRAGE® headgear arrangement of FIG. 1 when laid flat;

FIG. 3 is a schematic view of a set of visible indicia for indicatingthe headgear tension according to one embodiment of the invention;

FIGS. 4A and 4B are schematic views of visual indicia indicatingattainment of the desired headgear tension according to anotherembodiment of the invention;

FIG. 5 shows a necking portion on the headgear according to anotherembodiment of the invention;

FIGS. 6A to 6C show a further embodiment of the invention using relativemovement between an underlying and overlying portion of the headgear toindicate adjustment; and

FIGS. 7A to 7D show a clip and catch arrangement according to a furtherembodiment of the invention.

DETAILED DESCRIPTION OF ILLUSTRATED EMBODIMENTS

FIG. 1 shows the Applicant's prior art MIRAGE®full face mask 100 andheadgear 102 according to the Applicant's PCT Application WO 02/47749,which is incorporated herein by reference in its entirety.

The mask 100 is connected to a positive airway pressure (PAP) device orflow generator device (not shown) which provides breathable gas to themask for treatment of sleep apnea.

As shown in FIG. 2, the headgear 102 is constructed from a composite ofpolyurethane foam, loop material and hook material whose shape includesa pair of upper straps 20 and lower straps 30 and a generally triangularback portion 40. A piece of hook material 22 (e.g., such as Velcro®) isattached to the end of each of the four straps so that the straps may besecured to attachment points on the mask 100.

The hook material 22 may be ‘one way’ hook material so that it does notcatch on itself in the process of overlaying the straps before they arebrought into engagement.

In other, unillustrated, prior art arrangements, the straps 20, 30 maybe adapted to fit to a male clip connector which clips into a femaleconnector moulded into the mask frame of mask 100.

FIG. 3 shows a set of visible indicia 40 which may be printed onto orotherwise formed on the headgear 102, e.g., on the side straps 20, 30 orelsewhere on the headgear which is visible to the wearer in a mirror.

The indicia 40 comprise a set of ellipses of successively greater aspectratios, having vertical major axes. The indicia 40 may be labelled withtension settings, e.g., 1, 2, 3, 4, etc. In an embodiment, the indiciamay be labelled in mirror image so that they are readable by the wearerin the mirror. It should be appreciated that any suitable number ofellipses may be provided, and the ellipses may be spaced apart from oneanother in any suitable manner to indicate the setting.

In one alternative form of this embodiment, the setting labels mayindicate treatment pressures for which the corresponding headgearadjustment setting is recommended.

As the headgear strap (e.g., strap 20 of headgear 102) is placed undertension by tightening of the headgear (tension indicated by arrows), theheadgear material stretches in the direction normal to the ellipse axesand the ellipses become more circular. As the tension increases, firstone then the next ellipse become approximately circular, with the mostcircular ellipse indicating the tension setting. The wearer adjusts theheadgear until the desired tension setting is reached. That is, ellipse1 will become circular as tension is initially applied, ellipse 2 willbecome circular as more tension is applied, etc., with ellipse 4becoming circular at the highest tension setting.

In a further embodiment shown in FIGS. 4A and 4B, the indicia 140 areformed on the side straps 20, 30 by printing on the underlying materialof the headgear which is covered by a top layer. When the headgear isnot tensioned, the indicia 140 are obscured by the top layer (FIG. 4A),but when the desired headgear tension is reached the material of the toplayer becomes see-through and the indicia 140 become visible (FIG. 4B).

In an embodiment shown in FIG. 5, the headgear straps 20, 30 may includea necked portion 240 which narrows as the headgear tension is increased,and markings 250 may be provided adjacent the necked portion 240 forassessing the headgear tension. For example, the markings 250 provide areference for how narrow the necked portion 240 becomes upon tension.

FIGS. 6A to 6C illustrate a further embodiment of indicia 260 on theheadgear, in the form of a series of numerals or other symbolsindicating adjustment settings. The headgear also has a cover flap 270attached to the surface of the headgear strap (e.g., strap 20) along afold line 280. The flap obscures the indicia 260 when the headgear isuntensioned (FIG. 6A). The headgear material stretches as tension isapplied (tension indicated by arrows), with the relative movementbetween the indicia 260 and the cover flap 270 causing the indicia 260(e.g., numerals such as 1, 2, 3, etc.) progressively being uncovered asthe tension increases. The highest value uncovered numeral indicates theadjustment setting of the headgear. That is, the numeral 1 is uncoveredas tension is initially applied (FIG. 6B), numeral 2 is uncovered asmore tension is applied (FIG. 6C), etc., with the highest numeralbecoming uncovered at the highest tension setting.

In a further unillustrated embodiment, the indicia may comprise ancontact pressure film located between the rim and cushion of the mask,which changes colour with changes to the pressure on the seal as theheadgear is tightened or otherwise adjusted. The film may provide anindication of excessive pressure between the mask rim and the seal, andthe dispersion of that pressure. Examples of suitable contact pressurefilms include Pressurex tactile force indicating films from SensorProducts Inc of USA., and FilmLOC colour changing PET film from AustikTechnologies of USA.

Further headgear tension sensing means may include electrical sensorssuch as strain gauges or capacitance sensors which vary capacitancedepending on the distance between the capacitor plates. The sensorreadings are fed back to the flow generator, the processor of which isprogrammed with an algorithm for converting the signal into a tensionsetting for display on the flow generator display, and/or to provide anaudible or visible signal when the desired headgear tension is reached.

Further aspects of the invention relate to tightening mechanisms foradjustment of the headgear tension.

In one embodiment, the side straps 20, 30 may be connected to the maskby means of connectors which clip onto the mask frame of mask 100. Theconnection between the mask and the headgear connectors is adapted toprovide a visual, tactile or audible signal on reaching the desiredtension, and/or to release when the desired tension is exceeded.

FIGS. 7A to 7D schematically illustrate the operation of a clip 300provided to side straps 20, 30 of the headgear and a connector 330provided to the mask frame of mask 100, according to one embodiment ofthe invention.

The connector 330 (in the form of a female connector or clip receptacle)on the mask frame has a pair of opposed sides 332 each with inwardprojections 334 having a sloping front surface 336 and a more uprightrear surface 338.

The clip 300 has a body 302 and a pair of spring arms 304 with outwardprojections, i.e., front projection 306 and centre projection 308 whichform two recesses 310, 312 for receiving the projections 334 of theconnector 330.

The clip connection comprises a two stage latch arrangement in which theclip 300 clicks into the connector 330 on the mask in a first stageconnection in which the clip travels from the position of FIG. 7A tothat in FIG. 7D. The clip will provide two audible and/or tactileclicks, i.e., one as it moves from the position of FIG. 7B to 7C andanother when moving from the position of FIG. 7C to FIG. 7D.

For example, the clip 300 is engaged with connector 330 so that thesloping front surface 336 of the inward projections 334 engage the frontprojections 306 to flex the spring arms 304 inwardly towards the body302 until the front projections 306 move past the inward projections 334and into the position of FIG. 7C. As illustrated, the spring arms 304resiliently return to its initial position so that the inwardprojections 334 extend into the recess 310 and the front projections 306are retained by the rear surface 338. Further movement of the clip 300into the connector 330 causes the center projection 308 to ride over theinward projections 334 and into the position of FIG. 7D, in which theinward projections 334 extend into the recess 312.

The user then starts to tighten the headgear using the hook and looptabs on the side straps 20, 30. As the user continues to tighten theheadgear, the desired tension is reached and the spring arms 304 flexinwards so that the centre projections 308 ride past the projections 334of the connector and the clip releases to the position of FIG. 7C,emitting an audible ‘click’ or other cue for the user to stop tighteningthe headgear. The user therefore knows that the appropriate headgeartension has been reached and may then fasten the hook material tabs tofix the headgear in this adjustment setting.

The release tension for which the clip is designed may be controlled byvarying the stiffness of the spring arms 304 and the face angle andheight of the centre projections 308.

Optionally, the clip connectors may be interchangeable for similar clipshaving different release tensions, so that the headgear tension, may bevaried according to the treatment pressure and the patient'srequirements or preferences.

In an embodiment, the clip and connector may be structured such thatexcessive tension applied to clip allows the clip to completely releasefrom the connector. This quick release arrangement allows the patient toquickly remove the mask without manually flexing the spring arms, e.g.,for emergency situation, panic situation, claustrophobia, to preventexcessive tension applied to the straps, which could be uncomfortable oreven be harmful to the patient, etc. The release force may becontrolled, e.g., by varying the stiffness of the spring arms, the faceangle of the rear surface 338 of the inward projections 334, and/or theface angle of the rear surface of the front projections 306 (i.e., thesurface of the front projection 306 adapted to face and/or engage therear surface 338 when the clip is coupled to the connector). This quickrelease arrangement may be used with the multiple stage arrangementdiscussed above, or this quick release arrangement may be usedindependently.

Further tightening mechanisms according to embodiments of the inventioninclude the use of piezo materials or artificial muscles (e.g., deviceswhich contract lengthwise upon activation, for example of the types usedin robotic control systems) incorporated into the rear or side portionsof the headgear.

One example of a suitable artificial muscle apparatus is one or morepneumatic muscles incorporated into the headgear, i.e., tubular portionswhich contract lengthwise upon inflation, which may be inflated by airpressure from the flow generator. Examples of suitable air musclesinclude the Shadow Air Muscles available from Shadow Robot Company Ltdof UK and described at the websitehttp://www.shadowrobot.com/airmuscles.

Alternative artificial muscle apparatus which may be employed includeelectro-active polymers (EAPs) which contract upon application ofelectrical energy. Suitable electro-active polymers may includeelectronic or ionic, with electronic EAPs being preferred due to abilityto hold strain with DC activation and their relatively high actuationforces. Examples of electronic EAPs include ferroelectric polymers suchas poly(vinylidene fluoride), dielectric EAPs having low elasticstiffness and high dielectric constants (also known as electrostaticallystricted polymers or ESSPs), electrostrictive graft elastomers,electrostrictive papers, electro-viscous elastomers or liquid crystalelastomer (LCE) materials. Examples of ionic EAPs include ionic polymergels, ionomeric polymer-metal composites, conductive polymers or carbonnanotubes. Further discussion of each of these types of EAPs may befound in the article “ElectroActive Polymers—EAPs” at the website “The Ato Z of Materials”, by Dr. Yoseph Bar-Cohen, atwww.azom.com/details.asp?ArticleID=885, the contents of which articleare incorporated herein by reference.

A yet further automated headgear adjustment mechanism includes amagnetic adjustment mechanism, for example by varying the distancebetween magnets of constant field strength, such as permanent magnets,or by varying the field strength of electromagnetic apparatus.

A further headgear adjustment mechanism includes a bladder mounted on orincorporated in the headgear, or a plurality of such bladders atdifferent locations on the headgear, inflatable to increase the headgeartension. In one exemplary form, the bladder or bladders are inflated byair delivered by the flow generator. In one embodiment, the bladder orbladders are formed by comoulding with the material of the headgear.

In this specification, the word “comprising” is to be understood in its“open” sense, that is, in the sense of “including”, and thus not limitedto its “closed” sense, that is the sense of “consisting only of”. Acorresponding meaning is to be attributed to the corresponding words“comprise, comprised and comprises where they appear.

While the invention has been described in connection with what arepresently considered to be the most practical and preferred embodiments,it is to be understood that the invention is not to be limited to thedisclosed embodiments, but on the contrary, is intended to cover variousmodifications and equivalent arrangements included within the spirit andscope of the invention. Also, the various embodiments described abovemay be implemented in conjunction with other embodiments, e.g., aspectsof one embodiment may be combined with aspects of another embodiment torealize yet other embodiments. Further, each independent feature orcomponent of any given assembly may constitute an additional embodiment.In addition, while the invention has particular application to patientswho suffer from OSA, it is to be appreciated that patients who sufferfrom other illnesses (e.g., congestive heart failure, diabetes, morbidobesity, stroke, bariatric surgery, etc.) can derive benefit from theabove teachings. Moreover, the above teachings have applicability withpatients and non-patients alike in non-medical applications.

1. A headgear assembly for attachment to a patient interface thatdelivers breathable gas to a patient, comprising: a headgear bodyadapted to fit to the patient's head and has connection portions adaptedfor connection to the patient interface; adjustment means for adjustingsaid headgear; and indicating means responsive to an adjustmentparameter of the headgear for indicating attainment of a desiredadjustment setting of the headgear.
 2. A headgear assembly according toclaim 1, wherein said adjustment parameter to which said indicatingmeans is responsive is headgear tension.
 3. A headgear assemblyaccording to claim 2, wherein said indicating means comprises one ormore visible indicia which change responsive to the headgear tension. 4.A headgear assembly according to claim 3, wherein said visible indiciacomprise indicia which conforms to a predetermined shape to indicatesaid desired adjustment setting.
 5. A headgear assembly according toclaim 4, wherein said indicia change in elongation responsive to theheadgear tension.
 6. A headgear assembly according to claim 5, whereinsaid indicia include an ellipse which conforms to a substantiallycircular shape to indicate said desired adjustment setting.
 7. Aheadgear assembly according to claim 5, wherein said indicia comprise aset of indicia each adapted to indicate a different adjustment setting.8. A headgear assembly according to claim 7, wherein said set of indiciacomprises a set of ellipses of different aspect ratios.
 9. A headgearassembly according to claim 3, wherein said visible indicia are locatedon said headgear.
 10. A headgear assembly according to claim 3, whereinsaid visible indicia change in colour and/or shade to indicate saiddesired adjustment setting.
 11. A headgear assembly according to claim10, wherein said visible indicia comprise a portion of said headgearhaving an underlying material of a first appearance and an overlyingmaterial of a second appearance, and wherein said underlying materialbecomes visible upon application of a tension corresponding to saiddesired adjustment setting.
 12. A headgear assembly according to claim11, wherein said first and second appearances comprise differentcolours.
 13. A headgear assembly according to claim 11, wherein saidunderlying material becomes visible by movement of the overlyingmaterial to a position not overlying said underlying material.
 14. Apatient interface adapted to deliver breathable gas to a patient andadapted for attachment to the patient by means of adjustable headgear,comprising: indicating means responsive to an adjustment parameter ofthe headgear for indicating attainment of a desired adjustment settingof the headgear.
 15. A patient interface according to claim 14, whereinsaid indicating means is responsive to a pressure with which the patientinterface is retained against the patient.
 16. A patient interfaceaccording to claim 15, wherein said indicating means comprises one ormore visible indicia which change responsive to the pressure.
 17. Apatient interface according to claim 16, wherein said patient interfaceincludes a seal for sealing against the patient's face, and wherein saidindicating means co-operates with said seal.
 18. A patient interfaceaccording to claim 17, wherein said indicating means is responsive to acontact pressure applied to the seal.
 19. A patient interface accordingto claim 18, wherein said contact pressure is the contact pressurebetween the seal and the body of the patient interface.
 20. A patientinterface according to claim 19, wherein said indicating means includesa pressure-sensitive display between said seal and the body.
 21. Apatient interface according to claim 20, wherein said display changescolour in response to pressure. 22-37. (canceled)
 38. A method forcontrolling adjustment of headgear, comprising: adjusting the headgear;and visually indicating attainment of a desired adjustment setting ofthe headgear.
 39. The method according to claim 38, wherein visuallyindicating includes providing visible indicia structured to change inshape responsive to headgear tension.
 40. The method according to claim38, wherein visually indicating includes providing visible indiciastructured to become visible upon application of headgear tensioncorresponding to the desired adjustment setting.
 41. The methodaccording to claim 38, wherein visually indicating includes providing anecked portion to the headgear structured to narrow as headgear tensionis increased.
 42. The method according to claim 38, wherein visuallyindicating includes providing a contact pressure film to a mask providedto the headgear structured to change color as headgear tension isincreased. 43-46. (canceled)
 47. Headgear for a patient interface,comprising: at least one headgear strap; and an indicator provided tothe at least one headgear strap structured to indicate attainment of adesired adjustment setting of the headgear in response to headgeartension applied to the at least one headgear strap.
 48. Headgearaccording to claim 47, wherein the indicator includes visible indiciastructured to change in shape in response to headgear tension. 49.Headgear according to claim 47, wherein the indicator includes visibleindicia structured to become visible upon application of headgeartension corresponding to the desired adjustment setting.
 50. Headgearaccording to claim 47, wherein the indicator includes a necked portionstructured to narrow as headgear tension is increased.
 51. A patientinterface, comprising: a mask; and headgear according to claim 47provided to the mask. 52-56. (canceled)